1. Field of Invention
The present invention relates to cellulose-based fibers. More particularly, the present invention relates to cellulose-based fibers with a networked structure.
2. Description of Related Art
Cellulose fibers, or cellulosic fibers, are artificial fibers which were developed as early as the end of the 19th century. For example, natural celluloses are treated with a complicated process known as “cuprammonium process” to produce the purified (or regenerated) cellulose; alternatively, natural celluloses are chemically modified to yield the esterified celluloses such as cellulose acetate, and then, cellulose fibers are prepared from the resulting celluloses or cellulose derivatives. In the beginning of the 20th century, artificial fibers including rayon and acetate fibers have gained their positions in the market.
However, owing to the soaraway progress of the petrochemical technology, the low-cost and easy-to-produce synthetic fibers, such as nylons and polyester fibers, took the place of the artificial fibers as the mainstream products of the textile industry, by the middle of the 20th century.
Recently, the depleting reserves and rising prices of petroleum drive the textile industry to seek fibers other than synthetic fibers. Hence, cellulose-based fibers once again attract the research and development attention.
Conventional methods for preparing cellulose-based fibers include wet spinning, dry spinning and melt spinning.
Both wet spinning and dry spinning processes will use organic solvents such as carbon disulfide and dichloromethane. To prevent those organic solvents from damaging the environment, the solvents must be recycled and thereby inevitably increases the complexity and cost of the processes.
Melt spinning process involves in adding a great amount of a low molecular weight plasticizer (molecular weight no greater than 1000 D) in the esterified cellulose to obtain a melt-spinnable composition (masterbatch) which is later melt spun into cellulose-based fibers. Generally, the amount of the plasticizer in the melt-spinnable composition may be 50-90 wt %. However, low-molecular weight plasticizer usually cannot withstand the high spinning temperature, and hence the conventional spinning temperature is controlled under 260° C.; otherwise, the cellulose molecules would become yellowish-brown.
During the melt spinning process, spinning temperature is positively related to the flowability of the molten which, in turn, is positively related to the spinning speed. Therefore, owing to the limitation of the spinning temperature, the spinning speed of the cellulose-based fiber is less than commercially desirable. In addition, large amount of the plasticizer (about 50-90 wt %) often results in the phase separation between the plasticizer and the cellulose, thereby worsening the breaking tenacity of the resultant fiber. The above mentioned disadvantages hinder the melt spun cellulose-based fiber from commercialization.
In view of the foregoing, there exists an urgent need in the related art to provide a novel cellulose-based fiber capable of withstanding a higher spinning temperature and a method for preparing the same.